In recent years the historically minor expenses attributable to utilization of the mails have significantly increased as a result of both direct and indirect mailing costs. As these expenses continue to spiral upwardly, the mailing habits of major industries are coming under closer scrutiny with a view to controlling such expenses. In this connection, many major manufacturers of postage meters and systems, including the assignee of the present invention, have recently introduced lines of meterscale systems, which basically include a highly sensitive scale coupled to a postage meter which automatically prints the proper postage for franking the mailpieces weighed on the scale.
Other successful devices have been devised for reducing indirect mailing costs. For example, the assignee of the present invention recently introduced a system for remotely resetting postage meters to eliminate the labor costs which would otherwise be incurred for hand-carrying postage meters to the local Post Office for resetting purposes. Such a system is disclosed in U.S. Pat. No. 4,097,923, for example, assigned to the assignee of the present invention.
With the above thoughts in mind, it should be appreciated that there is a need in the marketplace to provide a suitable device for making a record of direct mailing costs on a current basis for cost analysis and other mail control purposes. In a typical office or corporate mailing room, a number of users have access to a single mailing machine and the postage meter associated therewith. In these situations, it is often desirable to account for the postage used by each person or department within the office. An automated system for providing this function is described in U.S. Pat. No. 4,286,144, issued to Pollak, Jr. et al., and assigned to the assignee of the present invention, the disclosure of which is hereby incorporated by reference.
In the apparatus of the above identified application, an encoder is shown for use with a postage meter. The encoder has a lever which is movable among a plurality of postage value selecting positions. The encoder includes framework adapted for removably mounting the encoder in operating relationship with respect to the postage meter, and includes devices for monitoring movement of the postage meter setting lever on the meter when the encoder is mounted in the operating relationship. The monitoring means includes apparatus includes devices for providing an electrical signal which varies in response to movement of the postage meter setting lever from one of the positions to another of the positions.
The encoder includes transducer assemblies which include a conventional variable linear potentiometer with a stationary linear resistance. As a postage meter setting lever is moved from one position to another, the resistance of the potentiometer varies, thus varying the value of the electrical signal.
The electrical signal generated by the potentiometer is converted by an analog to digital converter to a digital value. This value, as well as other data input by means of a keyboard to the accounting system, is stored in memory within the accounting system.
In practice, it is often desirable to maintain a record of a number of separate postage meters. These meters may be associated with diverse equipment, such as mailing machines, meter scales, electronic meters, and stand alone meters for use with the United States Postal Service (USPS) and for use with the United Parcel Service (UPS). In a given business environment, it is also often the practice to physically separate postage meters for use with different departments. A need therefore arose to handle a plurality of remote meters in one accounting system.
Moreover, for purposes of cost, effectiveness and efficiency, the required accounting system would preferably include a minimum number of components.
A common serial data bus to provide bidirectional communication among remote terminals and a central processing unit is well known in the art. Prior to the system of the present invention, however, separate driving circuitry was required to be associated with each of the external remote terminals. This practice of dedicating functionally identical driving circuitry, e.g. a line driver, a receiver/transmitter communications chip or other buffer, for each remote terminal is both costly and inefficient. The references discussed hereinbelow are illustrative of the prior art.
U.S. Pat. No. 4,041,469, issued to Jennings, shows a data processing system with a plurality of data entry terminals controlled by a CPU over a serial data bus. In this system, no universal synchronous/asynchronous receiver/transmitter (USART) is used nor is a priority interrupt controller provided to allow bidirectional communication between the CPU and individual terminals on a priority basis.
U.S. Pat. No. 4,106,104, issued to Nitta et al, teaches the use of a common bus connecting a plurality of devices, each of which is assigned a priority order. A detecting circuit is provided in one of the devices to detect a request signal. A unit for controlling the bus is connected thereto. This separate component receives requesting signals and sends an acknowledgement signal in response to the request signal. Although many interrupt requests may occur simultaneously, the same device will always be serviced first. No CPU or controller is used to arbitrate the priority of requesting devices.
U.S. Pat. No. 4,071,887, issued to Daly et al, discloses an integrated circuit synchronous adaptor (USART) for providing bidirectional communication. A bus is used to carry data to which a synchronization character or a fill character has been inserted or deleted. Parity generation and error checking is also performed by means of this bus. There is no mention, however, of a priority interrupt controller, nor is there any provision for a plurality of remote terminals.
U.S. Pat. No. 3,975,712, issued to Hepworth et al, shows receiving and transmitting circuitry for converting data in a serial format to parallel format. The communications interface allows data to be transferred asynchronously. There is no mention, however, of a priority interrupt controller.